Today, more than half of the human population lives in hive-like warrens called cities. Does this mean we are on the tipping point of becoming colony animals the way bees and ants did? It's not entirely impossible. We talked to scientists to find out whether urban humans are evolving into superorganisms.

Illustration of hive world Titanicus via EA

What Is an Individual?

Before we consider whether humans could form hive minds or colony societies, we first need a working definition of what it means to be an individual. But the whole idea of an "individual organism" is a lot messier than it seems. Washington University biologist Joan Strassmann, who has published papers on this topic with colleague David Queller, pointed out that it's incredibly hard to define an individual life form.

What, for example, makes a tree an individual? "Say it's an oak from an acorn — that's one organism," Strassmann said. "But if it's an aspen, the tree may not be separate. All the aspens in a grove may well be the same clone all coming up from the same root system with connections. Or those connections may be severed." She's referring to the way aspens grow from the same root system, the way many plants and slime molds do. Is your aspen an individual who shares a root system with its neighbors, or are all the trees who share the root system part of one "individual"? And this is just the beginning of the kinds of complexity you run into when trying to define life forms.

Plus, every person whom we think of as an individual actually evolved from simpler organisms that work cooperatively. Your body is a society of cells that function together to make you walk, clean your blood, and digest your food. And even the cells in your body are actually a collection of organelles, or tiny organs, like the energy-producing mitochondria. Scientists believe mitochondria were once single-celled creatures absorbed by larger cells that eventually became the familiar animal cells we know today, with their nuclei, organelles, and cytoplasm all wrapped up in a nice fatty membrane.

Strassmann and Queller use the term "evolution" to describe the process of becoming an individual organism. They emphasize that even our individuality is the result of a "social process" where many organisms that were previously individuals came together to make our multicellular sense of self. In a sense, we are already hives. Our bodies are comprised of millions of cells and microbes that work together selflessly, living and dying for the colony.

The Daughters Who Don't Leave Their Mothers

The origin of colony organisms, then, lurks in our own bodies. What led those first single-celled individuals to join up and become multicellular?

University of Minnesota biologists Mike Travisano and Will Ratcliff have been doing experiments that hint at the answer. They managed to turn single-celled yeast into multicellular organisms in just a few months, by breeding the yeast for what they call clumpers. First they put ordinary, single-celled yeast in a liquid medium where the cells that clumped together fell to the bottom more quickly. Then they bred these clumpers exclusively, and found that after 60 days — roughly 400 generations of yeast — they had simple multi-cellular organisms.

"Clustering is the first step," Ratcliff said. But what makes a single celled creature suddenly become a cluster? It's all about children who refuse to leave the nest. Yeast reproduce by "budding," forming a new daughter cell attached to the mother cell wall. "Normally when the daughter is mature it makes an enzyme that releases it," Ratcliff explained. "It looks like what happens is that daughter cell release is inhibited. The mothers remain attached to their daughter cells. That has the effect of making each cluster genetically identical." Multicellular organisms are, generally, packed with genetically identical cells — that's the case in your body, where every cell contains exactly the same DNA.

What Ratcliff and Travisano discovered was that eventually these clusters started behaving like individual organisms, with some cells committing suicide in a process called apoptosis. This seemingly grisly process is actually how multicellular organisms typically maintain their integrity. Older cells who aren't functioning optimally kill themselves off while younger ones continue to divide. Once a cell is willing to accept the death sentence from another in its cluster, you could argue that it is placing the survival of the organism over its own. Now, you have a colony organism that behaves like an individual.

Ratcliff and Travisano called their multicellular yeast individuals "snowflakes" due to their shapes (see image, with dead cells in red). When these snowflakes got big enough, one would break off from another. Eventually, the researchers found, these yeast were evolving as snowflakes rather than as single-celled organisms.

Through single-celled cooperation, new individual organisms had begun to form. Ratcliff and Travisano are continuing their experiments, trying to figure out whether the yeast snowflakes show other signs of organismality beyond apoptosis. They're trying to create multicellular green algae too.

Welcome to the Hive Mind

Now for the real question: What would inspire a group of multicellular organisms like ants or humans to form a superorganism? In their book The Superorganism, biologists Bert Hölldobler and E.O. Wilson argue that it's a complex process involving genetic evolution and environmental pressures. Generally a group of insects like bees will move from behaving as individuals to forming colonies when they are storing food (like honey or pollen) that comes from multiple sources. At that point, a colony has a better chance of surviving than an individual.

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This crude division is between a reproductive caste and a worker caste. In a typical bee colony, you have bees who care for the young, make honey, and forage for food — and that's just the beginning. Highly complex ant societies have many other castes, including things like farmer castes, garbage collector castes, and major fighter castes who are ants fed special foods to make them grow much larger than other ants in the colony.

What's truly amazing about these insect societies is that, despite the familiar terminology, they don't actually have a queen or ruling class. The queen is simply part of the reproductive caste, ensuring that the hive has a lot of genetic similarity (like our multicellular yeast) and continues to produce young. But each worker has evolved what Hölldobler calls an "algorithm" for making decisions about what jobs to do when, based on communicating with other insects and what caste it is currently in (bees, for example, pass through several castes as they age). There is no insect who is a master controller, who understands the totality of what's happening in the hive.

So colony societies or superorganisms evolve when some individuals give up their reproductive rights and create a division of labor. This scenario is often a response to environmental pressures, such as the need to store food from many sources and protect against many enemies at once. Colonies only survive because they are fitter than individuals in such environments, and there are examples of colony organisms gradually evolving back into individuals when the environment changes.

The Human Superorganism

Let's enter the realm of rank speculation and consider whether humans could evolve into a colony organism. It's a theme that crops up a lot in science fiction. Humans encounter a group where everybody behaves like they're part of an ant or bee colony: Each individual is prepared to sacrifice everything, including their lives, for the survival of the group. Star Trek's assimilating aliens, the Borg, are just one of many examples of how we've imagined such societies. But is human evolution actually moving in this direction?

While acknowledging that human cities could be considered colony-like, Strassmann was extremely dubious. "The things that would drive a human group to organismality would be suppression of conflict and an increase in cooperation," she said. "That could happen with higher relatedness. But right now there's far too much conflict." She pointed out that the best kinds of cooperative groups for forming an organism are clones, and humans are far from being genetic clones of each other. Plus, she asserted, "Just look at humans. All that conflict. I wish they were more like [colony] organisms."

Travisano, having witnessed the birth of multicellular yeast in just a few hundred generations, noted that "it's dangerous to say it's impossible." But at the same time, he and Ratcliff felt that the transition from individuals to colony might be easier with "smaller organisms," at least in the lab. They pointed out that in some ways humans are already colony organisms, if you consider the vast microbial ecosystems that exist in our guts and help us to survive.

Ultimately, though, they came up against the same issue Strassmann identified: When organisms make the leap from single cell to multicellular, or from multicellular to colony, they are usually genetically identical or very close.

What is common in all these social systems is a division of labor; and once this was evolutionarily rendered, it became incredibly successful. This is true for almost any society: once they reach a high division of labor, they have enormous successes due to division of labor. And the second thing, once a society becomes almost like an organism, it becomes very tightly interconnected.

But even Hölldobler admitted that humans experience too much conflict to form colonies — a behavior he calls maladaptive:

15,000 years ago we were hunter gatherers. We showed group cohesiveness and discrimination against other groups. It was adaptive. It was quite understandable that we evolved traits of group recognition, and making sure we recognized foreigners. This is my conviction that this is probably the early basis for our unfortunate xenophobic behavior that is still in us. It's a behavior that is now terribly maladaptive.

Does that mean our xenophobia is what keeps us individuated? Maybe. After all, we have many of the prerequisites required to become a colony organism. We have a highly complex division of labor, and we gather and store food from a variety of sources. We are even very close to each other genetically — as population biologists have pointed out, humans are very inbred.

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So what prevents us from crossing the threshold into forming superorganisms? Maybe we just haven't evolved beyond our primitive group differences enough. Or maybe part of what makes us humans, at least right now, is constantly navigating between colony consciousness and conflict. Either way, we're not likely to merge into hive organisms any time soon.